In recent years, technological innovation has acquired a fundamental role in the agri-food sector and in particular in food quality control. The development of technology allowed to improve the quality of the food before it is placed on the market. Recently, non-invasive techniques such as those operating in the THz spectral band were applied to the field of food quality control. In the laboratories of the ENEA centre in Frascati, close to Rome-Italy, has been developed a THz imaging system operating in reflection mode and an experimental setup able to measure both reflection and transmission of the samples in the frequency range between 18-40 GHz. With these two setups will distinguish rotten and healthy hazelnuts acquiring in real time both images of the fruit inside the shell by using the imaging system and the transmission data exploiting the 18-40 GHz system.

In recent years, the use of techniques based on electromagnetic radiation as an investigative tool in the agri-food industry has grown considerably, and between them, the application of imaging and THz spectroscopy has gained significance in the field of food quality control. This study presents the development of an experimental setup operating in transmission mode within the frequency range of 18 to 40 GHz, which was specifically designed for assessing various quality parameters of hazelnuts. The THz measurements were conducted to distinguish between healthy and rotten hazelnut samples. Two different data analysis techniques were employed and compared: a traditional approach based on data matrix manipulation and curve fitting for parameter extrapolation, and the utilization of a Self-Organizing Map (SOM), for which we use a neural network commonly known as the Kohonen neural network, which is recognized for its efficacy in analyzing THz measurement data. The classification of hazelnuts based on their quality was performed using these techniques. The results obtained from the comparative analysis of coding efforts, analysis times, and outcomes shed light on the potential applications of each method. The findings demonstrate that THz spectroscopy is an effective technique for quality assessment in hazelnuts, and this research serves to clarify the suitability of each analysis technique.

The electromagnetic radiation, in the range from IR to X-rays, is widely used in the field of art conservation and diagnostics. In the last few years a new interest was devoted to the longer wavelengths, in the so called “THz region” of the spectrum, due to the peculiar characteristics of the radiation in this spectral range, that make it ideal for applications in this field [1]: it's low photon energy and its ability to penetrate dielectric materials. This high penetration capabilities were used to demonstrate the possibility to detect artwork hidden under layers of other dielectric materials [2]-[4]. Making use of phase-sensitive techniques it is also possible to get information on the optical properties of the materials under study and to obtain images that include spectroscopic information about the sample [5]. Moreover, radiation in the THz range is strongly reflected and absorbed by water, and this feature can be used to study degradation in mural paintings and mosaics.